Question
I have a 15'x15' sun room which is facing north.I have about 150 orchids there.
I have 2 son agrow 430 W lamps, high pressure sodium,mercury lamp made by Philips.Light intensity at orchid high is average 400 f-c.
In winter I turn on 4 hours a day. My question is; Is there any other lamp type ? Because blooming is not as much as before ,say,2-3 years ago. Its humidity is 40- 80 % changing day and night depending on heater or A/C unit. Please advise.
Joon-Ho Kim

Answer
The sun room, like a greenhouse is quite at the mercy of lighting conditions outside.  There can be many cloudy days some years.  Your light intensity whould be closer to 1,500 f-c. at leaf level. Find a way to get the plants closer to the light source and increase the day length of light supplementation to about two hours less than the normal duration.  This time of year, I run my lights about 13 hours and increase the lighting daylength as natural daylength increase. I use a 430 W high pressure sodium light with plants 12- 24 inches from the light and currently 13 hours of daylength. This should also increase your growing temperature which should be 55 -80 degrees F. You should see some improved results with these changes.